Bilberry preparations have been used to improve poor night vision, light adaptation and photophobia, myopia and to prevent or retard diabetic retinopathy, macular degeneration and cataracts. Primarily the collagen-enhancing and antioxidant activities of bilberry provide a theoretical basis for these indications. Visual acuity and light adaptation A systemic review of 12 placebo-controlled trials (5 RCTs and 7 placebo-controlled non-randomised trials) concluded that the © 2007 Elsevier Australia
anthocyanosides from Vaccinium myrtillusYjere not effective for improving night vision; however, the authors point out that the potential therapeutic role of these constituents should not yet be dismissed because confounding factors and supportive auxiliary evidence exists (Canter & Ernst 2004). Four of the RCTs showed no positive effects for V. myrt///us anthocyanosides on outcome measures relevant to vision in reduced light whereas the fifth RCT and all seven non-randomised trials reported positive effects on outcome measures relevant to night vision. Seventeen other studies were located by Canter and Ernst but not included in the analysis because they did not contain a placebo group. Sixteen of those studies produced positive results on measures relevant to night vision in either healthy subjects or patients with a range of visual disorders and only one was negative.
The authors point out several confounding factors, in particular the wide range of doses, possible geographical variations in extract composition, choice of subject (generally healthy) and methods used to obtain and interpret electroretinograms, which varied between older and newer studies. For example, two of the negative RCTs tested the lowest dose levels of any of the trials: 36 mg daily for acute treatment and <48 mg for short-term treatment.
A significant improvement in visual performance has been demonstrated for bilberry extract in people with retinitis pigmentosa and hemeralopia (inability to see distinctly in bright light), suggesting that effects may be more pronounced in cases of impaired visual acuity (Gloria & Peria 1966, Junemann 1967). Glaucoma In one small study of eight patients, a single oral dose of 200 mg bilberry anthocyanosides was shown to improve glaucoma, as assessed by electroretinography (Caselli 1985).
Retinopathy In Europe, bilberry anthocyanoside extracts are recognised as highly effective in preventing or treating diabetic retinopathy, with clinical research supporting its use (Lietti et al 1976, Orsucci et al 1983, Perossini 1987, Scharrer & Ober 1981).
One double-blind study involving 40 patients with diabetic and/or hypertensive retinopathy showed that a dose of bilberry extract (Tegens™) equivalent to 160 mg anthocyanosides taken twice daily for 1 month significantly improved ophthalmoscopic parameters and angiographic parameters (Perossini 1987). Another study of 31 subjects with different forms of retinopathy (diabetic retinopathy, retinitis pigmentosa, macular degeneration or haemorrhage due to anticoagulant use) found that treatment with bilberry extract (Difrarel 100™) reduced vascular permeability and the tendency to haemorrhage in all patients (Scharrer & Ober 1981). A small open study by Orsucci et al of 10 subjects with diabetic retinopathy found that 6 months of
treatment with bilberry extract (Tegens™) equivalent to 240 mg anthocyanosides daily resulted in reduction or disappearance of haemorrhages and improvement in the retinal picture (Orsucci et al 1983 and reported in Blumenthal 2003). Myopia Uncontrolled trials report a beneficial effect of the extract on patients with myopia (Canter & Ernst 2004).
Cataract In practice, bilberry has been recommended to delay cataract progression A case series of 50 elderly subjects with early-stage cataract found that a combination of anthocyanosides extracted from bilberry and vitamin E slowed progression of lens opacities by 97% (Ulbricht & Basch 2005). Placebo-controlled trials are now required to confirm these results.
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